Over 10 million confirmed novel Coronavirus (Covid-19) cases globally and with more than 1,00,000 cases being detected every day across the world, there is an imperative to ramp up testing.
Various testing methods are being employed for this task and we have addressed them one by one in this article.
This article also focuses on innovative and rapid sample collection models.
The models such as Drive-through and Walk-through diagnostic testing to tackle the constraints imposed by social distancing, limited space and rapid consumption of personal protective gears from one to one medical consultation while maintaining worker’s safety.
Let us dive into the details of the tests being conducted. I will also talk about different models implemented for sample collection to fight Coronavirus.
Real-Time RT-PCR (Reverse Transcription-Polymerase Chain Reaction) Test
RT-PCR is one of the most reliable methods to detect, track and study the novel Coronavirus. It is used by most of the countries and in the past, this method has been also employed to detect Ebola and Zika Virus.
This technique delivers a reliable diagnostic in 3 hours, albeit on an average the laboratories take six to eight hours.
Initially, the cost of the test was 4500 INR. But since many governments have slashed the price of this test. Now, the test price could be anywhere between 2200 to 3500 INR.
A sample is collected from a person’s nose or throat, as the virus gathers in those areas, using a swab. The RNA is extracted from the collected samples using chemical substances. The extracted RNA contains the person’s RNA and the virus’s RNA(if present).
The RNA strand is converted to a DNA strand using a method called Reverse Transcription. It is important to convert the RNA to DNA since only DNA could be copied or amplified which will be quite useful for detecting the virus.
Then additional short fragments of DNA are added to the converted DNA for achieving twin objectives. Some of the added fragments get used for building DNA strands during amplification, while the others are used for adding marker labels to the strands which will be used to detect the virus.
The sample is then placed in an RT-PCR machine. The machine creates new, identical copies of the target sections of viral DNA, which is termed as a machine cycle.
A standard RT-PCR test usually runs for 35 cycles creating around 35 billion new copies of the target sections.
As new copies of the target sections are built, the attached marker labels release fluorescent dye. The machine tracks the amount of fluorescence present in the sample in real-time and when the level crosses a threshold it confirms the virus detection.
The fewer the cycles it takes to reach the threshold, the greater the severity.
Real-time RT-PCR cannot be used to detect past infections which is critical for understanding the development and the spread of the virus.
Rapid Antibody Testing
This technique is a kind of Serology test.
Serology tests are blood tests that look for the antibodies in the blood.
The presence of antibodies to Covid-19 virus indicates that a person had been previously infected with the virus and developed an immune response.
This technique is used to detect the previous infection in people who may have been exposed to the virus.
This method can give results in half an hour and cost around 600 INR.
This method provides an easier way to gauge the extent of the spread of the virus in a community.
A blood sample is taken from the finger and is placed in a template. Then the blood is examined for two types of antibodies -IgM (Immunoglobulin M) antibodies, which appear in the initial stage of the infection and IgG (Immunoglobulin G) antibodies, which are likely to develop in the later stage of the infection.
Rapid Antigen Testing
Rapid Antigen Testing belongs to a category of diagnostic tests.
It can quickly detect fragments of proteins found on or within the virus by testing samples collected from the nasal cavity using swabs. An antigen means a toxin or other foreign substance which induces an immune response in the body.
Similar to RT-PCR, this test too seeks to detect the virus and not the antibodies produced by the body but they can generally be produced at a lower cost than PCR tests.
This method can give results in half an hour and cost around 500 INR.
Samples are collected from the nasal cavity and tested for antigens which are found in the Covid-19 virus.
This medical test is carried out near the patient and does not require a laboratory setting.
This test is performed to obtain a quick diagnostic result.
Innovative Ways of Sample Collection
This innovative testing model was suggested by Jaemyung Lee, South Korean Governor of Gyeonggi Province.
He emphasized the need for scaled-up, minimum-contact testing and drawing attention to the safety of workers, limited space for social distancing and rapid consumption of personal protective gears from one-on-one medical consultation.
The first drive-through test was conducted at a city hall parking lot. The test included registration, screening test, swap collection and car disinfection.
A total of 4-8 persons are required to operate the drive-through.
On average, the process for each person took around 10 minutes whereas the previous testing procedures took 30 minutes.
The results of the test were delivered through text message to the patient within three days.
To make the process efficient, a standard was set that the patient must be the only person in the vehicle and he must make reservations prior to the visit.
While the drive-through model caters well to the patients having a private vehicle, they are not best suited for dense urban areas with fewer drivers and space constraints for car queues.
To address these problems, the hospitals came up with walk-through centres.
Walk-through centres are rows of plastic booths (similar to the size of a phone booth) fitted with intercoms, and attached gloves for healthcare workers inside the booth to interact with and collect samples from the patient.
This simple idea has enabled the healthcare workers to speed up the process since the booth does not need to be disinfected between the patients and also reduce the consumption of personal protective gears at the same time.
This innovative model has made low-contact testing possible and could also be deployed in dense urban areas owing to their small and mobile booths.
The importance of testing for Covid-19 could be gauged by the correlation of the fatality rates and the testing rates: A country that tests more, over time, will be in a better position to the contain the virus and reduce the death rates.
As more persons are detected with the virus daily, there is a need for testing aggressively and look beyond the conventional method of testing and collecting samples. Novel models such as Drive-through and Walk-through testing are the need of the hour and in the coming days, we will see more new unconventional and interesting models as the fight with coronavirus intensifies.